Who Needs Emotions? The Brain Meets the Robot

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from the primary taste cortex and the primary olfactory (pyriform) cortex;
from the amygdala; and from midbrain dopamine neurons. As Rolls documents,
damage to the caudal orbitofrontal cortex produces emotional changes, which
include the tendency to respond when responses are inappropriate (i.e., the
tendency of monkeys not to withhold responses to nonrewarded stimuli). Rolls
sees orbitofrontal neurons as part of a mechanism which evaluates whether a
reward is expected and generates a mismatch (evident as a firing of the nonreward
neurons) if the reward is not obtained when it is expected.
As Fellous and LeDoux note, decision-making ability in emotional situations
is also impaired in humans with damage to the medial prefrontal cortex
and abnormalities in the prefrontal cortex may predispose people to
develop fear and anxiety disorders. They suggest that the medial prefrontal
cortex allows cognitive information processing in the prefrontal cortex to
regulate emotional processing by the amygdala, while emotional processing
by the amygdala may influence the decision-making and other cognitive
functions of the prefrontal cortex. They then suggest that the prefrontal–
amygdala interactions may be involved in the conscious feelings of fear.
However, this neat division between the cognitive cortex and emotional
amygdala strikes me as too glib—both because not all parts of the cortex
give rise to conscious feelings and because human emotions seem to be inextricably
bound up with “cortical subtleties.”
Neuromodulation
We have now seen something of the crucial roles of the hypothalamus,
amygdala, and orbitofrontal cortex in the motivational system. In a similar
vein, Fellous (1999) reviewed the involvement of these three areas in emotion
and argued that the neural basis for emotion involves both computations
in these structures and their neuromodulation. It is thus a useful feature
of the present volume that Kelley’s analysis of motivation and emotion
emphasizes three widely distributed chemical signaling systems and their
related functions across different phyla. Following are some key points from
her richly detailed survey.
We first discuss dopamine, reward, and plasticity. In mammals, dopamine
is proposed to play a major role in motor activation, appetitive motivation,
reward processing, and cellular plasticity and may well play a major
role in emotion. In the mammalian brain, dopamine is contained in specific
pathways, which have their origins in the substantia nigra pars compacta and
the ventral tegmental area of the midbrain and ascend to innervate widespread
regions of striatal, limbic, and cortical regions such as the striatum,
prefrontal cortex, amygdala, and other forebrain regions. Studies in the